In existing analysis systems, e.g., for clinical chemical analysis of biological specimens, open reagent containers are used. An automatic pipetting device takes a small amount of a liquid reagent from the container and supplies it to a reaction cell. In each pipetting operation, an electromechanically driven arm guides the needle of the pipetting device to a reagent container, guides it in the container so as to remove a volume of reagent, lifts the needle out of the container and guides it to the reaction vessel to which the volume of reagent is to be supplied.
The capacity of a conventional reagent container is sufficient for a relatively large number (of the order of 20 to 2000) of such pipetting operations.
The use of open reagent containers has the following disadvantages:
The laboratory staff has to take each new reagent container out of its packaging, remove the closure and insert the open reagent container into the analysis system in place of an empty reagent container. Often a number of different reagents are needed at different times in the same analysis system. The use of open reagent containers therefore puts the laboratory staff to considerable trouble, because it demands from the staff a considerable amount of work.
When open reagent containers are used in rooms with relatively dry air, some of the reagent solution is lost through evaporation and, consequently, the concentration of the reagent increases with time. Conversely, when open reagent containers are used in rooms with relatively moist air or when water condenses during the use of cooled reagents, the volume of the reagent solution increases and, thus, its concentration decreases with time. Further, when open reagent containers are used, there is also an exchange of gas with the ambient air, and this exchange causes ageing, consequently changing the reagent. All the aforementioned changes in the reagent, particularly in the changes in its concentration, reduce the accuracy of the analisis results. Attempts to obviate this problem by enclosing the entire reagent container in relatively complicated packaging have only been partially effective.
One object of the invention is to provide a closure or cap overcoming these disadvantages.